Investigating the influences of intermolecular interactions on viscoelastic performance of pressure-sensitive adhesive by FT-IR spectroscopy and molecular modeling

A strong, silk protein-inspired tissue adhesive with an enhanced drug release mechanism for transdermal drug delivery

In transdermal drug delivery system (TDDS) patches, achieving prolonged adhesion, high drug loading, and rapid drug release simultaneously presented a significant challenge. In this study, a PHT-SP-Cu2+ adhesive was synthesized using polyethylene glycol (PEG), hexamethylene diisocyanate (HDI), trimethylolpropane (TMP), and silk protein (SP) as functional monomers which were combined with Cu2+ to improve the adhesion, drug loading, and drug release of the patch. The structure of the adhesion chains and the formation of Cu2+-p-π conjugated network in PHT-SP-Cu2+ were characterized and elucidated using different characterization methods including FT-IR, 13C NMR, XPS, SEM imaging and thermodynamic evaluation. The formulation of pressure-sensitive adhesive (PSA) was optimized through comprehensive research on adhesion, mechanics, rheology, and surface energy. The formulation of 3 wt.% SP and 3 wt.% Cu2+ provided superior adhesion properties compared to commercial standards. Subsequently, the peel strength of PHT-SP-Cu2+ was 7.6 times higher than that of the commercially available adhesive DURO-TAK® 87-4098 in the porcine skin peel test. The adhesion test on human skin confirmed that PHT-SP-Cu2+ could adhere to the human body for more than six days. Moreover, the drug loading, in vitro release test and skin permeation test were investigated using ketoprofen as a model drug, and the results showed that PHT-SP-Cu2+ had the efficacy of improving drug compatibility, promoting drug release and enhancing skin permeation as a TDDS. Among them, the drug loading of PHT-SP-Cu2+ was increased by 6.25-fold compared with PHT, and in the in vivo pharmacokinetic analysis, the AUC was similarly increased by 19.22-fold. The mechanism of α-helix facilitated drug release was demonstrated by Flori-Hawkins interaction parameters, molecular dynamics simulations and FT-IR. Biosafety evaluations highlighted the superior skin cytocompatibility and safety of PHT-SP-Cu2+ for transdermal applications. These results would contribute to the development of TDDS patch adhesives with outstanding adhesion, drug loading and release efficiency. STATEMENT OF SIGNIFICANCE: A new adhesive, PHT-SP-Cu2+, was created for transdermal drug delivery patches. Polyethylene glycol, hexamethylene diisocyanate, trimethylolpropane, silk protein, and Cu2+ were used in synthesis. Characterization techniques confirmed the structure and Cu2+-p-π conjugated networks. Optimal formulation included 3 wt.% SP and 3 wt.% Cu2+, exhibiting superior adhesion. PHT-SP-Cu2+ showed 7.6 times higher peel strength than DURO-TAK® 87-4098 on porcine skin and adhered to human skin for over six days. It demonstrated a 6.25-fold increase in drug loading compared to PHT, with 19.22-fold higher AUC in vivo studies. α-helix facilitated drug release, proven by various analyses. PHT-SP-Cu2+ showed excellent cytocompatibility and safety for transdermal applications. This study contributes to developing efficient TDDS patches.

Water-compatible cross-linked pyrrolidone acrylate pressure-sensitive adhesives with persistent adhesion for transdermal delivery: Synergistic effect of hydrogen bonding and electrostatic force

Poor skin adhesion and mechanical properties are common problems of pressure-sensitive adhesive (PSA) in transdermal drug delivery system (TDDS). Its poor water compatibility also causes the patch to fall off after sweating or soaking in the application site. To solve this problem, poly (2-Ethylhexyl acrylate-co-N-Vinyl-2-pyrrolidone-co-N-(2-Hydroxyethyl)acrylamide) (PENH), a cross-linked pyrrolidone polyacrylate PSA, was designed to improve the adhesion and water resistance of PSA through electrostatic force and hydrogen bonding system. The structure of PENH was characterized by 1H NMR, FTIR, DSC, and other methods. The mechanism was studied by FTIR, rheological test, and molecular simulation. The results showed that the PENH patch could adhere to human skin for more than 10 days without cold flow, and it could still adhere after sweating or water contact. In contrast, the commercial PSA Duro-Tak® 87-4098 and Duro-Tak® 87-2852 fell off completely on the 3rd and 6th day, respectively, and Duro-Tak® 87-2510 showed a significant dark ring on the second day. Mechanism studies have shown that the hydrogen bond formed by 2-ethylhexyl acrylate (2-EHA), N-vinyl-2-pyrrolidinone (NVP), and N-(2-Hydroxyethyl)acrylamide (HEAA) enhances cohesion, the interaction with skin improves skin adhesion, and the electrostatic interaction with water or drug molecules enhances the ability of water absorption and drug loading. Due to the synergistic effect of hydrogen bonds and electrostatic force, PENH can maintain high cohesion after drug loading or water absorption. PENH provides a choice for the development of water-compatible patches with long-lasting adhesion. STATEMENT OF SIGNIFICANCE: Based on the synergistic effect of hydrogen bonding and electrostatic force, a hydrogen-bonded, cross-linked pyrrolidone acrylate pressure-sensitive adhesive for transdermal drug delivery was designed and synthesized, which has high adhesion and cohesive strength and is non-irritating to the skin. The patch can be applied on the skin surface continuously for more than 10 days without the phenomenon of "dark ring", and the patch can remain adherent after the patient sweats or bathes. This provides a good strategy for choosing a matrix for patches that require prolonged administration.

Design of a tulobuterol patch with improved mechanical properties: effect of transdermal permeation enhancers on the release process of metal ligand-based acrylic pressure-sensitive adhesives

The aim of this study was to design a tulobuterol (TUL) patch with good penetration behavior and mechanical properties. Particular attention was paid to the effect of transdermal permeation enhancers on the release process of metal ligand-based acrylic pressure-sensitive adhesive (AA-NAT/Fe3+). The type and dosage of the enhancers were screened by in vitro transdermal penetration in rat skin. The optimized formulation was evaluated in a pharmacokinetic study in rats. Furthermore, the molecular mechanism by which Azone (AZ) improves the release rate of TUL from AA-NAT/Fe3+ was investigated by FT-IR, shear strength test, rheological study, and molecular simulation. As a result, the optimized formula using AA-NAT/Fe3+ showed better mechanical properties compared to commercial products. Meanwhile, the AUC0-t and Cmax of the optimized patch were 1045 ± 89 ng/mL·h and 106.8 ± 28.5 ng/mL, respectively, which were not significantly different from those of the commercial product. In addition, AZ increased the mobility of the pressure-sensitive adhesive (PSA) rather than decreasing the drug-PSA interaction, which was the main factor in enhancing TUL release from the patch. In conclusion, a TUL transdermal drug delivery patch was successfully developed using metal-coordinated PSA, and a reference was provided for the design of metal-coordinated acrylic PSA for transdermal patch delivery applications.

Fe(III)-coordinated N-[tris(hydroxymethyl)methyl]acrylamide-modified acrylic pressure-sensitive adhesives with enhanced adhesion and cohesion for efficient transdermal application

Pressure-sensitive adhesives are critical to the product's safety, efficacy, and quality in transdermal drug delivery systems. However, many defects of transdermal patches (e.g., insufficient adhesion, patch displacement, and "dark ring" phenomenon) remain. Herein, the N-[tris(hydroxymethyl)methyl]acrylamide (NAT)-modified acrylic pressure-sensitive adhesive coordinated with Fe(III) (AA-NAT/Fe³⁺) was creatively proposed. Results demonstrated that the adhesiveness and cohesiveness of the optimized AA-NAT/Fe³⁺ were higher by 1.8- and 9.7-fold, respectively, than those of commercially available DURO-TAK® 87-4098 due to the hydrogen bonding interaction of NAT-skin interface and coordination of NAT-Fe³⁺. Moreover, compared with that of DURO-TAK® 87-4098, the adhesion time of AA-NAT/Fe³⁺ on the human forearm was remarkably prolonged, and no "dark ring" phenomenon was observed for AA-NAT/Fe³⁺ after removal. After clonidine (CLO) was loaded into AA-NAT/Fe³⁺, controlled drug release and a drug transdermal behavior were endowed for CLO@AA-NAT/Fe³⁺in vitro and in vivo. AA-NAT/Fe³⁺ still maintained superiority in adhesion and cohesion properties after CLO loading. These observations would contribute to the development of pressure-sensitive adhesives with outstanding adhesion and cohesion for transdermal patches. STATEMENT OF SIGNIFICANCE: This N-[tris(hydroxymethyl)methyl]acrylamide-modified acrylic pressure-sensitive adhesive coordinated with Fe(III) has enhanced adhesion and cohesion properties, which provide a simple but effective strategy to solve the problems (e.g., insufficient adhesion, patch displacement, and "dark ring" phenomenon) in existing transdermal patches.

Evaluation of the Structural Modification of Ibuprofen on the Penetration Release of Ibuprofen from a Drug-in-Adhesive Matrix Type Transdermal Patch

This study aimed to evaluate the effect of chemical modifications of the structure of active compounds on the skin permeation and accumulation of ibuprofen [IBU] from the acrylic pressure-sensitive adhesive used as a drug-in-adhesives matrix type transdermal patch. The active substances tested were ibuprofen salts obtained by pairing the ibuprofen anion with organic cations, such as amino acid isopropyl esters. The structural modification of ibuprofen tested were Ibuprofen sodium salt, [GlyOiPr][IBU], [AlaOiPr][IBU], [ValOiPr][IBU], [SerOiPr][IBU], [ThrOiPr][IBU], [(AspOiPr)₂][IBU], [LysOiPr][IBU], [LysOiPr][IBU]₂, [PheOiPr][IBU], and [ProOiPr][IBU]. For comparison, the penetration of unmodified ibuprofen and commercially available patches was also investigated. Thus, twelve transdermal patches with new drug modifications have been developed whose adhesive carrier is an acrylate copolymer. The obtained patches were characterized for their adhesive properties and tested for permeability of the active substance. Our results show that the obtained ibuprofen patches demonstrate similar permeability to commercial patches compared to those with structural modifications of ibuprofen. However, these modified patches show an increased drug permeability of 2.3 to even 6.4 times greater than unmodified ibuprofen. Increasing the permeability of the active substance and properties such as adhesion, cohesion, and tack make the obtained patches an excellent alternative to commercial patches containing ibuprofen.